T-34C AIRCRAFT SYSTEMS FAMILIARIZATION
Trim tabs allow the pilot to correct an unbalanced flight condition without exerting continuous
pressure on the primary controls. They are small moveable tabs on the trailing edge of each
primary control surface.
Trim tab controls are located at the forward end of the left console in both cockpits. Position of
the rudder trim knob, elevator control wheel and aileron control wheel present a logical display
for use. Rotation of trim knob or wheels will effect movement of the trim tab through chain and
cables and push-pull tubes and will move controls in both cockpits simultaneously. The rudder
trim tab knob incorporates a numbered circular scale representing degrees of deflection.
Elevator and aileron trim tab wheels utilize an adjacent plastic window indicating degrees of
Elevator Trim Tabs
Elevator trim tabs are designed to impart a clockwise rotation to the fuselage to offset torque
effect or "left-turning tendency." On preflight with elevator trim set at "0" the right tab will be
4½º up and the left tab will be 4½º down. As the trim control is moved in the cockpit, the trim
tabs will move up or down accordingly, but will remain with a 9° split between the two tabs.
With movement of the control stick and elevator, the elevator tabs will remain in their adjusted
position in relation to the elevator.
Rudder Trim Tab
When the rudder trim tab knob is set "0," the tab is aligned with the rudder. Rotating the trim tab
knob deflects the trim tab and the rudder is deflected in the desired direction. Moving the
rudders with the pedals causes the tab to move in the same direction, thereby creating artificial
feedback or feel. This is referred to as antiservo action.
Aileron Trim Tabs
When the aileron trim tab wheel is set at "0," the left trim tab is aligned with the trailing edge of
the left aileron. The right tab is set by the manufacturer or maintenance action, and is not
adjustable. Both ailerons move due to mechanical connection. When moving the ailerons with
the control stick each trim tab moves in the opposite direction (lag) of its aileron, acting as a
lever to assist the aileron movement. This is referred to as servo action.
Strakes and Ventral Fins
The strakes are an extension of the horizontal stabilizer forward alongside the empennage. The
ventral fins form a "V" beneath the empennage. The strakes and ventral fins limit the aircraft's
spin turn rate.
FLIGHT CONTROL SYSTEMS